The invention relates to an adjusting device for the brake shoes of inside shoe brakes which is assigned to mutually adjacent ends of two brake shoes connected to one another via a tension spring, and which has adjusting members which each engage on one of the brake shoe ends and are mounted on a carrier and which are jointly adjustable in mutually opposite directions by means of an actuating member which is arranged rotatably in a threaded bore extending in the carrier between the adjusting members in parallel with the drum axis and which is supported with a conically tapered endpiece between the adjusting members.
An adjusting device of this genera type is already known from German Patent Specification 567,716. It affords the advantage of a uniform setting or adjustment of brake shoes.
The carrier of this adjusting device forms a guide housing which is built on to the brake carrier and in which are arranged displacably as adjusting members two mutually opposite support pins, each articulated with their outer end on the web end of a brake shoe and with their inner end being in engagement with the circumference of a conically tapered endpiece of an actuating member. This actuating member is arranged rotatably by means of a threaded shank in a threaded bore extending in the guide housing between the support pins in parallel with the axis of the brake drum. At the same time, the inner ends of the support pins are made wedge-shaped and each engage positively into one of engagement grooves formed on the circumference of the conically tapered endpiece of the actuating member at equal angular intervals along generatrices.
In order to set or adjust the brake shoes, the actuating member has to be rotated correspondingly, and as a result of its threaded guide it shifts in the axial direction and at the same time presses the support pins apart correspondingly transversely in relation to the drum axis. This adjusting device, because of its guide housing fixed to the brake carrier, is suitable only for those drum brakes of which the brake shoes are mounted pivotably on the brake carrier (Simplex brakes). At the same time, the production of the guide housing involves a high outlay in manufacturing terms, in that it has to be equipped with special guide bores for the support pins and therefore has to be produced and machined as a shaped body. Finally, the mounting of the device is complicated and time-consuming, since both the guide housing has to be built on to the brake carrier and the support pins have to be connected pivotably to the brake-shoe webs.
An object on which the invention is based is to improve an adjusting device of the above-noted type in such a way that it is characterized by the simplest possible design and can also be installed both in Simplex brakes and in dual servo-brakes.
According to the invention, this object is achieved by providing an arrangement wherein the adjusting members are levers which are pivotable about respective axes extending perpendicular relative to the axis of the actuating member and which are supported on one edge of a respective brake-shoe web so as to surround the same.
The design according to the invention of the adjusting members as levers articulated on the carrier allows a compact and simple carrier design as a sheetmetal shaped article. Because the levers are each supported with their front end on one edge of a brake shoe web and also surround this edge laterally, it is possible merely to attach the adjusting device on to the brake shoe webs in order to arrange it in inside shoe brakes. Its mounting can therefore be carried out completely independently of the brake carrier and without the aid of any fastening means. Accordingly, it can also execute brake-reinforcing movements of brake shoes. In comparison with the design according to German Patent Specification 567,716, an embodiment of the invention wherein the conically tapered endpiece of the actuating member is rotationally symmetrical affords the important advantage of a continuous brake shoe adjustment.
Further advantageous features of preferred embodiments of the invention are the subject of the dependent claims.
In addition to the adjusting device according to German Patent Specification 567,716, U.S. Pat. No. 3,977,500 --FIG. 5--already makes known an adjusting device which, in a generally similar way to the invention, has two adjusting levers which each surround with their one end a respective edge of a brake shoe web and which are supported with their other end on an actuating member. These adjusting levers are arranged within a guide housing fastened to the brake carrier and can be adjusted there from the outside by means of an actuating member.
The use of this adjusting device is therefore likewise restricted to Simplex brakes.
Similar conditions are present in an adjusting device according to U.S. Pat. No. 2,609,066. Its adjusting levers are made double-armed, being respectively articulated with their outer end on the end of a brake shoe web, with their inner end on one another and with their middle part on a brake carrier. Their inner lever ends connected to one another in an articulated manner interact with an adjusting screw.
Apart from the fact that the mounting of this adjusting device can be carried out only with difficulty, its use in dual servo-brakes is likewise impossible because of the articulation of the adjusting levers on the brake carrier.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.